DEVELOPMENT OF INTEGRATED PEST MANAGEMENT PROGRAMS TO REDUCE METHYL BROMIDE FUMIGATIONS FOR CONTROL OF INSECTS IN POSTHARVEST STRUCTURES
Location: Stored Product Insect Research Unit
Title: Variation in predator foraging behavior changes predator-prey spatio-temporal dynamics
Submitted to: Functional Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 27, 2011
Publication Date: November 1, 2011
Citation: Nachappa, P., Margolies, D.C., Nechols, J.R., Campbell, J.F. 2011. Variation in predator foraging behavior changes predator-prey spatio-temporal dynamics. Functional Ecology. 25(6): 1309-1317. http://dx.doi.org/10.1111/j.1365-2435.2011.01892.x.
Interpretive Summary: Predators, or insects that eat other insects, can be used to manage pest insect populations, but to be successful they need to be able to find prey distributed within a crop before prey populations build to levels that cause economic damage. One approach to increase the effectiveness of predators in pest management is to use artificial selection to improve certain predatory traits. A predatory mite species was selected to develop strains with three different traits: 1) increased tendency to leave a group of prey, 2) increased rate at which prey are eaten, and 3) increased number of eggs laid for each prey eaten. In greenhouse tests where prey were distributed among a number of plants, these three strains gave similar overall suppression of prey on plants, but differed in number of predators produced and ability to find the prey on plants. While in the short-term these different predator traits were equally effective, differences among predator strains in ability to track prey movement among plants suggest that long-term differences in prey suppression are likely to occur. Use of artificially selected predators provided a unique ability to address fundamental questions about how predators interact with their prey, and to address practical questions about the potential for artifical selection to improve use of predators in pest management.
1. Foraging underlies the ability of all animals to acquire essential resources and, thus, provides a critical link to understanding population dynamics. A key issue is how variation in foraging behavior affects foraging efficiency and predator-prey interactions in spatially-heterogeneous environments. However, there is very little quantitative information available on this topic.
2. We evaluated the impact of variation in predator foraging on population dynamics of the predatory mite, Phytoseiulus persimilis, and its prey, the twospotted spider mite, Tetranychus urticae, in a simple patchy environment.
3. Through artificial selection, we obtained predator lines with high levels of prey consumption, conversion efficiency, or dispersal, with which we examined the effect of these traits on temporal and spatial patterns of predators and prey.
4. We initiated the experiments in a 24-plant landscape which contained two discrete prey patches (i.e., prey-infested plants) under two initial predator-prey population ratios (1:10 and 1:30). Predators were introduced into one of the prey patches and were left to forage for 24 days.
5. Initial predator-prey ratio did not affect the impact of the selected lines on prey population growth, but the unselected line had a much greater impact on prey numbers at the high (1:10) than the low (1:30) initial ratio.
6. Prey population growth was similar among the three selected lines; but the high conversion efficiency line produced the most predators and had the highest predator-prey ratio and the high consumption and high dispersal lines were intermediate. The unselected line showed the least growth and lowest predator-prey ratio throughout the experiment.
7. Predators and prey were each individually aggregated, but the high conversion efficiency and high dispersal lines showed stronger spatial association and correlation with prey, while the high consumption line was less closely associated or correlated with the prey.
8. These results indicate there may be multiple, equally effective strategies by which predators exploit prey in simple patchy landscapes, but suggest that the long-term dynamics may not be stable under all of these strategies.